Laminate having textured wear surface and process of preparation

ABSTRACT

A product having a textured surface thereon (and its process of manufacture) is disclosed wherein the textured surface is obtained by relieving the stress in pre-stressed polymeric chips that have been distributed as a single layer throughout a polymeric layer superimposed on a substrate.

CROSS-REFERENCE TO RELATED APPLICATION

This is a continuation of application Ser. No. 918,762, filed Jul. 27,1992 now abandoned which is a continuation-in-part of U.S. patentapplication Ser. No. 615,133, filed Nov. 19, 1990 now abandoned.

FIELD OF THE INVENTION

The present invention relates to decorative laminates that are suitableas surface coverings for floors, walls, etc., and, more particularly,the invention is directed to a decorative laminate having surfacetexture for improving the visual appeal and wear resistance of thelaminate.

BACKGROUND OF THE INVENTION

Decorative laminates used as surface coverings for floors are well-knownin the art and have achieved broad use in both domestic and commercialenvironments. These laminates in the form of sheet material composed ofa resinous polymer composition, e.g., polyvinyl chloride, laminated to asuitable substrate, e.g., a fibrous backing sheet, have been used formany years as sheet flooring. To illustrate, many methods and processessuch as mechanical embossing, chemical embossing or inlaying have beenutilized to provide contrasting surface finishes and thereby impartdecorative effects to the sheet flooring. For example, U.S. Pat. Nos.3,000,754 and 4,456,643 each discloses different techniques or means formaking floor covering products such as floor tiles or sheet flooringhaving decorative surface effects. A goal common for all these productsis to combine attractive surface decorative effects from an aestheticviewpoint with substantial wear resistance from a functional standpoint.

In U.S. Pat. No. 3,000,754, the embossed effect is obtained by hotpressing at least two PVC resins of different molecular weights. Thehigher molecular weight resin has a greater tendency to relax in adirection normal to the plane of the surface covering to provide thetextured effect.

In U.S. Pat. No. 4,456,613, the laminate has an embossed surfacecomposed of raised segments containing PVC particles adjoining recessedsegments devoid of PVC particles. Similar articles are disclosed in U.S.Pat. Nos. 4,599,264 and 4,450,194.

In U.S. Pat. No. 4,405,657, a non-skid plastic floor covering isdisclosed wherein slip-resistant particles are embedded in a curedplastic matrix with the uppermost layer of particles protruding from thematrix. A clear or translucent wear layer coats the outer surface.

U.S. Pat. Nos. 4,816,317 and 4,816,319 disclose the use of discreteportions of a thixotropic plastic material containing solid material toprovide the raised elements of the textured surface.

U.S. Pat. No. 4,348,447 discloses a non-skid plastic flooring product inwhich inorganic particles are applied to the adhesive surface of aplastic matrix and then embedded into the matrix by pressure. However,particles applied in this manner do not penetrate uniformly throughoutthe matrix. Furthermore, to obtain complete bonding of the particles tothe plastic matrix, a thin coating is applied over the surface. Thisstep tends to fill the interstitial areas between raised particles andreduce the textured effect on the surface. The use of such particlesalso tends to obscure any underlying decorative portion that may beimposed on a substrate that supports the plastic matrix containing theparticles.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a decorativelaminate having a textured wear surface that avoids the difficultiestypically associated with the use of particles that are pressed into thesurface of the laminate.

It is also an object of the present invention to provide the texturedwear surface in a cost-effective process that minimizes the requiredsteps while still insuring success.

According to the present invention, there is provided a decorativelaminate having a textured wear surface suitable as a floor or wallcovering comprising:

1) a substrate, optionally having a printed image thereon, comprisingPVC foamable plastisol gel on a felt carrier;

2) a layer of a substantially transparent synthetic organic polymersuperimposed on the substrate and preferably adhered or bonded to thesubstrate; and

3) a plurality of polymeric chips distributed throughout and embedded inthe organic polymer layer, the chips having been stressed prior toembedding and relaxed thereafter to provide a textured effect to thesurface of the laminate.

Specifically, the polymeric chips, that are embedded in the organicpolymer layer, are "stress-induced" chips that have been stretchedlengthwise, while relatively solid after cooling from the molten stage,to an extent of at least twice its original length; and then, afterbeing embedded or at least partially embedded, laid flat in the softorganic polymer layer and coated, the stressed chips are permitted torelax or contract, usually by heating the structure at or above theoriginal stretching temperature but below the melting temperature of theorganic polymer. During the heating, the chips tend to contract or "pop"to provide the desired textured effect on the surface of the productwhile still remaining coated with the wear resistant polymeric coating.

To insure that all chips are completely embedded in the polymeric layerbefore the heat treatment, it is recommended that a thin coatingcompatible with the polymeric layer (usually the same composition as thepolymeric layer) be applied over the chips prior to relaxing to protectthem and the surface of the structure from wear and dirt and also tofill any potential dirt-collecting recesses that may have developedduring the production process.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 is a cross-sectional view depicting the arrangement of elementsand structural features of the product of the invention;

FIG. 2 is a schematic view of a process and equipment that may be usedto produce the "stress-induced" polymeric chips; and

FIG. 3 is a schematic view of a process and equipment that are used inthe manufacture of the product of the invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 depicts the decorative laminate product 10 of the invention incross-section. The laminate is composed of three basic layers: thecarrier layer 16, the substrate layer 11 and the surface or wear layer18 that includes the texture-producing chips 14 embedded therein. Anoptional layer 12 composed of a thin clear coat of plastisol may beapplied to the surface of the substrate layer 11 if the surface isprinted with rotogravure or other printing techniques that impart colorand pattern to the product.

The substrate 11 is preferably a foamed plastisol gel. The substrate 11comprises anywhere from 10 to 30 mils of the approximately 80-100 milsthick product.

It should be understood that any of the substrates and/or carriersnormally employed in the surface covering field may be employed toprepare the laminate of this invention. It should be a strong, durableand flexible material. Thus, any woven, felted or solid sheet ofsynthetic or natural material may be used as layer 16.

The surface or wear layer 18 is usually, although not necessarily,applied in two steps; one step before the particles 14 are deposited andthe second step after the particles 14 are deposited. The wear layer 18may be anywhere from 20 to 40 mils thick, usually about 25 to 30 mils;and the chips 14 are from 2-20 mils in their shorter dimension, usuallyabout 10 mils thick.

The resin component of the substrate 11, the wear layer 18, and theparticles 14 is preferably a vinyl resin, that is, a polymeric materialobtained by polymerizing compounds containing at least one --CH═CH₂radical. Useful vinyl resins include homopolymers, such as polyvinylchloride, polyvinyl acetate, polyvinyl propionate, polyvinyl butyrate,polymerized vinylidene chloride, polymerized acrylic acid, polymerizedethyl acrylate, polymerized methyl acrylate, polymerized propylacrylate, polymerized butyl acrylate, and the like; copolymers of theabove with each other such as vinyl chloride-vinyl acetate copolymer,vinylidene chloride-vinyl chloride copolymer, methyl methacrylate-vinylchloride copolymer, methyl acrylate-ethyl acrylate copolymer, ethylacrylate-butyl acrylate copolymer, and the like and copolymers of theabove with other monomers copolymerizable therewith, such as vinylesters, including vinyl bromide, vinyl fluoride, vinyl choroacetate,vinyl alkyl sulfonates, trichloroethylene and the like; vinyl etherssuch as vinyl ethyl ether, vinyl isopropyl ether, vinyl chloroethylether and the like; cyclic unsaturated compounds such as styrene,chlorostyrene, coumarone, vinyl pyridine and the like; maleic andfumaric acid and their derivatives such as diethyl maleate, dibutylfumarate and the like; unsaturated hydrocarbon such as ethylene,propylene, butylene and the like; allyl compounds such as allyl acetate,allyl chloride, allyl ethyl ether, and the like; conjugated andcross-conjugated unsaturated compounds such as butadiene, isoprene,chloroprene, 2,3-dimethylbutadiene-1,3, divinyl ketone and the like. Themonomers listed hereinabove are useful in preparing copolymers with avinyl resin and can be used as modifiers in the polymerization, in whichcase they may be present in an amount of a few percent, or they can beused in larger quantities, up to as high as 40 percent by weight of themixture to be polymerized. If desired, a mixture of vinyl resins can beused in preparing the layer 18 for use in the invention.

A plasticizer for the vinyl resin is also frequently present in thesecompositions. Suitable plasticizers for the vinyl resin include estertype plasticizers such as tributyl phosphate, dioctyl phthalate,dipropylene glycol dibenzoate, phenyl phosphate, dibutyl tartrate, amyltartrate, butyl benzyl benzoate, dibutyl sebacate, dioctyl adipate,didecyl adipate and the like, rubbery plasticizers, such asbutadiene-styrene copolymer, butadiene-acrylonitrile copolymer, and thelike, and other materials which function as plasticizers, such asepoxidized drying oils, aromatic hydrocarbon condensates and the like.Where certain flexible soft vinyl resins are used in formulating theselayers, such as polymers containing large proportions of ethyl acrylate,no plasticizer is needed. However, in most instances, a plasticizer isessential in order to impart the necessary properties of flexibility tothe dried film.

The thickness of the relatively flat, substrate 11 will depend to alarge extent upon the particular product to be made and the particularsubsequent use for which it is intended. Normally, a thickness in therange of from about 10 mils to about 90 mils is satisfactory.

The chips 14 may be prepared by the process shown schematically in FIG.2. Specifically, a polymeric film 21, usually of polyvinyl chloride,about 10 inches wide and anywhere from 30-40 mils thick, preferablyabout 40 mils thick, is extruded through the die 22 of a standard meltextruder, not shown. The film 21 is cooled to a temperature just aboveits glass transition temperature (about 50° C.) by passing over aconventional, cooled calender roll 23 and then the film is drawn toabout one-fourth its original thickness by passing through the nip ofroll 23 and stretching roll 24. The stressed film is then led to aslitter, grinder or dicer 25 and sieve 26 to provide "stressed"particles or chips.

If the chips 14 are formulated from the same polymer as constitutes thepolymeric layer 18, the polymer of the chips 14 would have a highermolecular weight than the polymer of layer 18, to enable the chips 14 to"pop" within the softened layer 18 and produce the textured effect. Ithas been noted that the chips 14 in the textured surface of the productof the present invention tend to display curved or rounded edges whencompared to the sharp edged chips that provide the textured surface ofprior art products.

The chips 14 are preferably unfilled but may be filled with smallamounts, i.e., up to about 5%, of the usual fillers (talc or the like)as long as the amount used does not interfere with the "popping" of thethermoplastic chip. For some very fine fillers, interference with"popping" may not occur with amounts as high as 50%. However, the amountof filler must be controlled so as not to interfere with the visualdecorative effect desired for the ultimate product.

It should also be understood that this invention is not intended toprovide slip-resistant patches in a thermoplastic floor covering. Nor isit intended to have more than a single layer of plastic coveredparticles or "popped" chips providing the desired decorative texturedsurface over the entire product.

Furthermore, the chips, after "popping" to provide the textured surface,while still being covered by a 3-20 mil polymeric coating, should exposea surface that is of substantially uniform hardness. Thus, whereas a"slip resistant" surface, as disclosed in U.S. Pat. No. 4,348,447,require particles having a Mohs hardness of at least about 4, thetextured surface of this invention composed of chips and recesses orinterstitial areas (including the covered surface of the "popped" chips)would display a Mohs hardness of much less than 4, preferably no higherthan 3.

A decorative printed image 12 may be applied to the plastisol coating 18on the surface thereof after it has been gelled. Printing isconventional and paints and inks normally used for application of adecorative design to a vinyl film or layer are used. The composition ispreferably formulated so that the binder of the ink contains anappreciable quantity of a vinyl resin. Suitable vinyl resins includevinyl chloride polymer, vinyl chloride-vinyl acetate copolymer, vinylchloride-vinyl propionate copolymer, vinyl butyrate polymer, vinylidenechloride polymer, vinylidene chloride-vinyl chloride copolymer,copolymers of vinyl chloride and vinylidene chloride with esters ofmaleic and fumaric acid, such as dimethyl, diethyl, and dibutyl maleateand fumarate, and the like. Extender resins, such as nitrocellulose oracrylic polymers, can be employed as a portion of the binder of the inkor paint.

The decorative printing composition contains pigments according to thecolors desired and is preferably formulated as a solution in a solventsuch as cyclohexanone, methyl ethyl ketone, methyl isobutyl ketone andthe like.

The decorative printing composition can be applied to the surface of thegelled plastisol coating in any way appropriate for producing theparticular decoration desired. Any of the rotary graphic art printingprocesses, such as rotogravure, offset printing or lithography, can beused. If desired, the design can be applied by conventional blockprinting technique.

In FIG. 3, a schematic view of the process of this invention, a feltcarrier or other backing sheet 11, about 25 mils thick, is fed throughthe nip and around the cylindrical rolls 31 and 32 of a reverse rollcoater or knife-over-roll or other similar coater. A clear, viscous,foamable plastisol layer 18 is applied to the top surface of the backingsheet 11 to a thickness of 5-20 mils, preferably about 10 mils. Theplastisol coating 18 is gelled (typically with exposure to a temperatureof 240°-290° F.) from the heated drum 32 or by passing the combinationthrough an oven.

Optionally, the surface of the gel 18 may be printed with rotogravure orother printing techniques (not shown) to impart color and pattern andalso to provide an opportunity for chemically embossing selected areasof the surface by inhibiting foam expansion. Thereafter, a thin clearcoat of plastisol may be applied (2-5 mils) to protect the gravure printduring subsequent processing.

After an additional small amount, 0.5-3 mils, of the plastisol coatingor pattern print is applied through a feeding device (not shown), thecoated sheet is passed beneath the outlet of a Shilling or similar chipfeeder 33, equipped with a screen and an oscillator blade and containingthe stressed chips 14. The chips 14 are deposited in excess into the"adhesive" or plastisol layer 18 to provide full coverage. Any chips notadhering to the plastisol "adhesive" are subsequently removed using anair knife and vacuum take-off 42.

The combination of base layer 11 and top layer 18 with the particles 14in the adhesive layer is then heated and planished around drum 34maintained at a temperature of about 320° F. and equipped with infeedand outfeed pressure rolls 40 and 41. The primary purpose of this stepis to lay any "standing" particles 14 flat, smooth the surface forsubsequent coating and gel the chips 14 in place.

After passing through the cooling rolls 35, 36 and 37, the gelledlaminate 10 may be further clear coated with another application at 15to the surface of the planished chips 14 of about 10 mils of theplastisol used to prepare layer 18 at the reverse roll coater shown at38. This last coating controls (along with the degree to which chips 14have been stressed originally and the various processing temperatures)the ultimate degree of surface texture and fills any void areas.

The sheet is then passed into the oven 39 maintained at a temperatureabove which the chips were originally stressed but below the meltingtemperature of the chips, i.e., 365°-385° F. This exposure is sufficientto expand the foam, effect any chemical embossing, fuse the plastisolwear layer and permit the chips to become substantially unstressed andto return to approximately their original dimensions. In so doing, thechips 14 tend to "pop" as shown in FIG. 1 and provide the laminate withthe desired textured surface. The laminate is then permitted to cooland, thus, provide the textured surface covering product of thisinvention.

In another, more general embodiment, a thin plastisol film (2-5 mils)may be applied at 18 to a release paper or other temporary carrier 11.The plastisol film is permitted to gel and then, as in the previouslydescribed process, a plastisol coating or pattern print may be appliedto a thickness of 0.5-3 mils. Thereafter, the stressed chips are appliedat 33 in excess to provide full coverage; and any chips not adhering aresubsequently removed using an air knife and vacuum take-off 42.

The structure 10 with the chips 14 applied is heated and planishedaround drum 34 with the outfeed and the infeed pressure rolls 40 and 41associated therewith, to lay any standing chips flat, smooth the surfacefor subsequent coating and gel the chips in place.

The structure 10 with the stressed chips 14 therein may then be removedfrom the temporary carrier 11 and subsequently used to impart a texturedsurface to any other structure by a lamination technique.

What is claimed:
 1. A wear-resistant laminate having a textured surface,said textured surface having raised and lowered surface areas,comprising:(a) a substrate layer of a foamed plastisol gel having athickness of 10 to 30 mils; (b) a wear layer of a synthetic organicpolymer superimposed over and directly in contact with the completesurface of said substrate layer; (c) a single layer of unfilledthermoplastic polymeric chips within said wear layer, each chipseparated by interstitial areas from its neighboring chips; and (d) thewear layer having a portion above said single layer of chips and saidinterstitial areas, said portion having a substantially uniformthickness of 3-20 mils, wherein said raised surface areas are alignedwith said chips and said lowered surface areas are aligned with saidinterstitial areas.
 2. A product as in claim 1 wherein the polymercomponent of said substrate layer of a foamed plastisol gel, saidthermoplastic polymeric chips and said wear layer in which the chips aredistributed is polyvinyl chloride, the polyvinyl chloride of the chipsbeing of highest molecular weight.
 3. A product as in claim 1 wherein adecorative image is applied to said surface of said substrate layer.